On 11/28/22 21:39, Steven Rostedt wrote:
> On Fri, 25 Nov 2022 22:20:23 +0100
> Daniel Bristot de Oliveira <bristot@xxxxxxxxxx> wrote:
>
>> @@ -1308,6 +1315,8 @@ static void notify_new_max_latency(u64 latency)
>> */
>> static int run_osnoise(void)
>> {
>> + bool preempt_disable = test_bit(OSN_PREEMPT_DISABLE, &osnoise_options);
>> + bool irq_disable = test_bit(OSN_IRQ_DISABLE, &osnoise_options);
>
> bool irq_disable = test_bit(OSN_IRQ_DISABLE, &osnoise_options);
> bool preempt_disable = IS_ENABLED(CONFIG_PREEMPT) &&
> !irq_disable && test_bit(OSN_PREEMPT_DISABLE, &osnoise_options);
Ooops again, that is not exactly what I wanted, because...
>> struct osnoise_variables *osn_var = this_cpu_osn_var();
>> u64 start, sample, last_sample;
>> u64 last_int_count, int_count;
>> @@ -1335,6 +1344,14 @@ static int run_osnoise(void)
>> */
>> threshold = tracing_thresh ? : 5000;
>>
>> + /*
>> + * IRQ disable also implies in preempt disable.
>> + */
>> + if (irq_disable)
>> + local_irq_disable();
>
> if (preempt_disable)
>> + preempt_disable();
>> +
>> /*
>> * Make sure NMIs see sampling first
>> */
>> @@ -1422,16 +1439,21 @@ static int run_osnoise(void)
>> * cond_resched()
>> */
>> if (IS_ENABLED(CONFIG_PREEMPT_RCU)) {
>> - local_irq_disable();
>> + if (!irq_disable)
>> + local_irq_disable();
>> +
>> rcu_momentary_dyntick_idle();
>> - local_irq_enable();
>> +
>> + if (!irq_disable)
>> + local_irq_enable();
>> }
>>
>> /*
>> * For the non-preemptive kernel config: let threads runs, if
>> - * they so wish.
>> + * they so wish, unless set not do to so.
>> */
Then I end up cond_resched'ing here in the non-preemptive kernel.
>> - cond_resched();
>> + if (!irq_disable && !preempt_disable)
>> + cond_resched();
But I also want to avoid this cond_resched if preempt_disable is set.
So, I will merge both things:
- change the preempt_disable assignment to check !irq_disabled, like:
/*
* Disabling preemption is only required if IRQs are enabled, and the options is set on.
*/
preempt_disable = !irq_disable && test_bit(OSN_PREEMPT_DISABLE, &osnoise_options);
- change the preempt disabled if to
if (IS_ENABLED(CONFIG_PREEMPT) && preempt_disabled)
preempt_disable();
I tested with both preemption models (preemptive and not preemptive) and it works fine.
am I missing something?
-- Daniel
>> last_sample = sample;
>> last_int_count = int_count;
>> @@ -1450,6 +1472,14 @@ static int run_osnoise(void)
>> */
>> barrier();
>>
>> + /*
>> + * Return to the preemptive state.
>> + */
>
> if (preempt_disable)
>> + preempt_enable();
>> +
>
>> + if (irq_disable)
>> + local_irq_enable();
>
> -- Steve
>
>> /*
>> * Save noise info.
>> */
